1. Field of the Invention
The present invention relates to an X-ray phototaking apparatus for taking, an X-ray image of an object on a sheet film by utilizing radiation.
2. Related Background Art
FIG. 13 is a schematic view of a conventional X-ray phototaking system for X-ray phototaking of the chest or abdomen and the like of an object person, wherein shown are an X-ray source 101 including an X-ray tube; an object 102; an X-ray phototaking apparatus 103 for X-ray phototaking on an incorporated sheet film; and a rack 104 for supporting said apparatus.
FIG. 14 is an external view of the X-ray phototaking apparatus 103 shown in FIG. 13, wherein shown are a supply magazine 105 stocking unexposed sheet films; a receiving magazine 106 stocking exposed sheet films; and a chest plate 107 where the chest or abdomen and the like of the object person is to be contacted. Inside said chest plate there is provided a phototaking part, to which a sheet film is supplied from the supply magazine 105. On said phototaking part an intensifying screen is fixed for example by adhesion and the like. By X-ray irradiation while the sheet film is in close contact with the intensifying screen, the X-ray image of the object is formed on the sheet film. The exposed film is discharged from the phototaking part to the receiving magazine 106.
FIG. 15 shows an example of the internal structure of a conventional X-ray phototaking apparatus in a cross-sectional view. In a state shown in FIG. 15, a sheet film F has been fed to the phototaking part and has been brought into close contact with the intensifying screen. In the order from the X-ray source side, there are provided a chest plate 107 to which the body of the object is to be contacted; a grid 108 for eliminating scattered rays which are generated when X-rays pass through the body of the object and which deteriorate the image quality; a detector 109 of a phototimer, for detecting the intensity of the X-rays transmitted through the object and thereby controlling the irradiating time and the like of the X-rays for obtaining an appropriate exposure on the sheet film; and a front intensifying screen 111 and a back intensifying screen 112 each of which generates visible light in response to the X-rays and between which the sheet film F is sandwiched. The front intensifying screen 111 is fixed, for example by adhesion and the like, to a front support member 110, while the back intensifying screen 112 is likewise fixed to a back support member 113.
A sheet film separated by an unrepresented separating mechanism from the supply magazine 105 is supplied to the phototaking part through supply means including rollers 114, 115 and a guide plate 117 etc.
Feeding of the sheet film to the phototaking part, the back support member 113 and the back intensifying screen 112 are in a broken-line position. After the sheet film F is fed into a position between the front intensifying screen 111 and the back intensifying screen 112 in this state, the back support member 113 supporting the back intensifying screen 112 is moved toward a direction A by the rotation of a cam 118 and pressed to the front support member 110, whereby the sheet film F is tightly sandwiched between the front intensifying screen 111 and the back intensifying screen 112. The X-ray phototaking is conducted while the sheet film F is maintained in close contact with the intensifying screens 111 and 112 in the phototaking part. After said phototaking operation, the back support member 113 is moved opposite to the direction A to release the sheet film F from the contact with the intensifying screens 111 and 112, and the exposed sheet film F is stored in the receiving magazine 106.
The X-ray phototaking operation is generally conducted in the above-explained manner. It is desirable to provide a plurality of intensifying screens for converting the X-rays into the visible light which are different in sensitivity, light-emitting characteristics etc. and is suitably selected according to the position of the body of the object to be photographed. For example, an intensifying screen with a high sharpness and a wide latitude is used for the chest, while an intensifying screen of a high sensitivity is used for the abdomen. Also in the frontal chest radiography, so-called sensitivity-compensating intensifying screen, having a lower sensitivity in the areas corresponding to lung lobes is sometimes used, because the X-ray transmission is higher in the lung lobe regions than in the mediastinum at the center of the body. As an example of such X-ray phototaking apparatus employing some kinds of intensifying screens, the Japanese Patent Laid-open Application No. 3-174531 disclosed a phototaking apparatus which incorporates three kinds of intensifying screens and is provided with a so-called screen changer, a mechanism for selectively setting one of three kinds of intensifying screens in the phototaking part.
However, in the conventional radiographic phototaking apparatus in which a kind and a set of front and back intensifying screens is fixed in the phototaking part, it has been unable to select, in a single phototaking apparatus, optimum intensifying screens according to the part of the body to be photographed such as chest, abdomen or waist and the like, the front or lateral image taking even for a same part of the body, the age or the physique of the object person, or the purpose of inspection such as precision inspection or group inspection. Therefore, for selecting optimum intensifying screens in order to obtain X-ray images matching the different objectives, it has been necessary to employ plural X-ray phototaking apparatuses, or to effect phototaking operation utilizing plural cassettes respectively incorporating intensifying screens of different characteristics.
On the other hand, the phototaking apparatus with the above-explained screen changer inevitably becomes bigger and heavier because of the mechanism for intensifying screen exchange. For this reason there is required a wide X-ray room, and such apparatus has been unsuitable for a limited space such as the wagon for the X-ray phototaking used for group inspection. Also such phototaking apparatus can only incorporate a limited number of intensifying screens, so that it has not necessarily been possible to select the optimum intensifying screen matching the desired phototaking conditions.